A reaction furnace utilizing high-temp steam and recirculated heat source to separate mercury and crack dioxin and organic substances contained in waste includes a first combustion chamber having a burner for producing high-temp hot gas, which is sent to a second combustion chamber for heating a reaction chamber and a high-temp steam generator therein. High-temp steam produced by the high-temp steam generator is introduced into the reaction chamber for decomposing or distilling waste being treated. Gas mixture produced in the reaction chamber is discharged to a gas mixture treatment system for separation. Fuel gas and fuel oil separated from the gas mixture are introduced into the burner for producing the high-temp hot gas, and waste water separated form the gas mixture is led to the high-temp steam generator for producing the high-temp steam. And, soil in the waste that has been treated is discharged via a discharge outlet.